Can Blender use Virtual Memory?
All software uses virtual memory automatically. Operating systems usually take care of that. When you run out of RAM your storage devices are used. That is called paging. Storage drives are extremely slow compared to RAM so things slow down a lot when this happens. 20-30 seconds is extremely unimaginably fast for a render though. My renders, for example, would take 20 - 30 hours and even more per 4K still image if I rendered them on a single PC. Renders take lots of time. This cannot be solved by an answer on Stack Exchange I am afraid.